A hydroformylation reaction that is generally well known as OXO reaction is the process for producing a linear (normal) and branch-(iso) aldehyde, in which the olefin is added with one carbon atoms by react all kinds of olefins and synthesis gases (CO/H2) in the presence of a metal catalyst and a ligand.
All kinds of aldehydes that are synthesized by OXO reaction are modified into acids and aldehydes that are aldehyde derivatives, and alcohols through an oxidation or a reduction reaction. Also, they can be modified into various acids, aldehydes and alcohols comprising long alkyl group through the oxidation or reduction reaction after a condensation reaction, such as aldol, and the like. Those aldehydes, alcohols, and acids are being used as a raw material for solvents, additives, and plasticizers.
The representative example of hydroformylation is to produce octanol (2-ethylhexanol) from propylene using a rhodium based catalyst. Octanol is mainly used as a raw material for PVC plasticizer, such as DOP (dioctyl phathalate), and also as an intermediate raw material for synthetic lubricants, surfactants, and the like.
Propylene is injected with a catalyst into OXO reactor using synthesis gases (CO/H2) to produce normal-butylaldehydes and iso-butylaldehydes. The produced aldehyde mixture is transferred to a separator along with catalyst mixture to separate into hydrocarbon and catalyst mixture, and then the catalyst mixture is circulated into the reactor and the hydrocarbon is transferred to a stripper. The hydrocarbon in the stripper is stripped by fresh synthesis gases to recover non-reacted propylene and synthesis gases into OXO reactor and transfer butylaldehydes to a fractionation column thereby separating normal-butylaldehydes and iso-butylaldehydes, respectively. Normal-butylaldehydes of the fractionation column bottom is transferred to a hydrotreated reactor, and then adding hydrogen produces n-butanol. Alternatively, normal-butylaldehydes are introduced into an aldol condensation reactor to produce 2-ethylhexanal through a condensation and dehydration reaction, and then transferred to the hydrotreated reactor to be octanol (2-ethylhexanol) by adding hydrogen.
The hydroformylation reaction may be performed in a continuous, semi-continuous or batch type, and a typical hydroformylation reaction is a gas or liquid circulation system. It is important for the hydroformylation reaction to increase the reaction efficiency by smoothly contacting the starting materials that are composed of a liquid phase and gas phase. For this reason, conventionally the continuous stirred tank reactor (CSTR) that stirs for evenly contacting the liquid phase and the gas phase inside the reactor was mainly used. In addition, U.S. Pat. No. 5,763,678 discloses the hydroformylation method, in which the circulation is used instead of the stirring by applying the reactor that is a type of loop. However, those methods have a limit to the improvement of the hydroformylation reaction efficiency and also single reactor cannot produce the satisfactory aldehyde product, so that the residence time of the reaction is made to be longer, or more than two reactors are connected in series thereby producing the product that has a required level.
In addition, the hydrogenation process of aldehydes generally uses the reactor, in which nickel-based or copper-based solid hydrogenation catalyst is filled inside the reactor. There are two ways for performing the reaction, such that the starting aldehydes are evaporated to perform the reaction in a vapor phase, or the starting aldehydes are introduced into the reactor as a liquid to perform the reaction in a liquid phase.
However, there is a problem that the selectivity of the reaction is reduced by generating an undesirable side reaction, such as esterification, acetal formation, etherification, and the like in the above reaction, even though the above catalysts types, the vapor phase, or the liquid phase are applied.